实现Square类，让其继承自Rectangle类，并在Square类增添新属性和方法，在2的基础上，在Square类中重写Rectangle类中的初始化和打印方法

实现Square类，让其继承自Rectangle类，并在Square类增添新属性和方法，在2的基础上，在Square类中重写Rectangle类中的初始化和打印方法

 #import <Foundation/Foundation.h>

 @interface Rectangle : NSObject{

     int width;

     int height;

 }

 @property int width,height;

 -(int) area;

 -(int) perimeter;

 -(void)setWidth:(int)w andHeight:(int)h;

 -(void)print;

 @end

 #import <Foundation/Foundation.h>

 @interface Rectangle : NSObject{

     int width;

     int height;

 }

 @property int width,height;

 -(int) area;

 -(int) perimeter;

 -(void)setWidth:(int)w andHeight:(int)h;

 -(void)print;

 @end

 #import <Foundation/Foundation.h>

 #import "Rectangle.h"

 @interface Square : Rectangle

 -(void) setSide:(int) s;

 -(int)side;

 -(int)area;

 -(int)perimeter;

 -(void)print;

 @en

 #import "Square.h"

 @implementation Square

 -(void) setSide:(int) s{

     [self setWidth:s andHeight:s];

 }

 -(int) side{

     return width;

 }

 -(int)area{

     return width*width;

 }

 -(int)perimeter{

     return *(width+height);

 }

 -(void) print{

     NSLog(@"side width: %d",width);

 }

 @end